ABR audio coding systems are designed to allocate a variable amount of data to different temporal sections (notably frames) of audio data, while maintaining, in average, an overall constant bitrate. An ABR audio coding system makes use of a so called bit reservoir to achieve this goal. Typically side information or additional metadata is transmitted together with the core audio data within the same bitstream. The amount of additional metadata may vary over time, thereby impacting the bit allocation control mechanism for maintaining, in average, an overall constant bitrate.
The present document addresses the technical problem of providing an improved bit allocation scheme for ABR audio coding systems which encode varying amounts of metadata along with audio data. In particular, a bit allocation scheme is described, which improves the perceived audio quality of the encoded audio data in a temporally consistent manner, even in cases where varying amounts of metadata are to be encoded along with the audio data.